Black Oil

[LordAnthony]

I bought a new minor recently and the first thing I did was to change the oil and the filter as it was very black.
A few weeks regular commuting (26 mile round trip) later and it was black again so I did another change, together with a magnetic sump plug, thinking perhaps that it had been a while and there was a lot of crud floating about. This was last week and I can see that it's gradually getting darker again.

Does this indicate a problem? Should I just keep changing the oil and filter until it's got rid of all the carbon or is there something serious afoot?

My other Minor leaks quite a bit of oil so I always have to top it up but it consequently has nice golden oil at all times. And less rust underneath.

[alex_holden]

The piston rings/bores may be a little worn but I wouldn't worry about it too much if the oil going black quickly is the only symptom. Perhaps try doing a compression test, first with dry bores and then with a squirt of oil in each bore. If the compression is a lot better 'wet' that would suggest worn rings.

The other possibility that comes to mind is perhaps a lot of gunk built up in the sump because the previous owner didn't bother with regular oil changes and only used it for short journeys, and now your regular commute is causing the gunk to dissolve. Adding a can of engine flush and running it for a while before you change the oil will help, but if it's really thick, the best thing would be to take the sump off and scrape it out.

[billlobban]

Personally I would avoid the flushing oil it will just dislodge all of the 'gunk' that has built up over the years and may make any compression problem you may have even worse

[linearaudio]

If you want to get mucky, the sump drops easily in-situ, and you will undoubtably get a better result by scraping/washing down the accessible bits of crank area than any amount of engine flush will have! Similarly, the rockers and rocker cover can be cleaned to great advantage.
Any additive will by definition put more rubbish into the oil which can lead to problems, as the flushing is done through the whole oil flow, so some debris will be dislodged after the filter stage!

[bmcecosse]

As above - if bothered scrape out the sump and rocker cover - avoid the flushing additives! It will be fine though to just leave as is. But do make SURE the spring and pressure plate are present and correct inside the filter casing - are they there ?

[LordAnthony]

It's a spin-on filter so should be ok from that point of view.
When I took the rocker cover off to adjust the gaps a couple of weeks ago there was indeed a load of crud under there, which I cleaned out so I will do the same with the sump and see what happens.
At least I know it's nothing terminal and can wait a little longer.

[bmcecosse]

That is the advantage of the screw on filter - otherwise I prefer the original. I wouldn't worry about the sump too much - any 'crud' will just stay there on the floor - and if/when you remove it - you may just start up some oil leaks!

[lynda]

I'm guessing you're talking about Eric If so then my Dad never drove him very far - an occasional 6 mile round trip into work and back, and the branch meetings / runs in the summer. He'd also been standing for a while before my Dad bought him, so that'd presumably add to the crud build up. I'm relieved to hear it's nothing too serious though, and that Eric is getting well looked after

[bmcecosse]

While back I bought a 1275 Marina engine. The 'oil' that ran out when I opened the drain plug was like black paraffin - thin/runny - and the sump when removed was almost 2" deep in thick black smelly sludge. Yet the crank bearings and the pistons/rings are near perfect! So as long as there is something there to get pumped round - these engines are remarkably robust.

[LordAnthony]

Hi Lynda - yes it is indeed Eric. Tell your dad he's doing fine. I've just come back inside after fitting an electronic ignition to him which worked a treat.